Isotopes of an element have the same:
- A.Atomic number but different mass number
- B.Mass number but different atomic number
- C.Number of neutrons but different number of protons
- D.Number of protons and the same number of neutrons
Correct answer
Explanation
The correct answer is A, atomic number but different mass number. Isotopes are atoms of the same element, so they have the same number of protons and therefore the same atomic number, but they carry different numbers of neutrons, which makes their mass numbers differ. Hydrogen has three isotopes, protium, deuterium and tritium, and chlorine occurs naturally as chlorine-35 and chlorine-37. Option B is wrong because atoms with the same mass number but different atomic numbers are isobars, such as argon-40 and calcium-40. Option C is wrong because atoms with the same number of neutrons but different numbers of protons are called isotones. Option D is wrong because atoms with the same number of protons and the same number of neutrons are simply identical atoms of one isotope, not isotopes of each other. Because isotopes differ only in neutrons, they share the same chemical behaviour and differ in physical properties such as density and radioactivity.
Read the full article: Atomic Structure and Periodic Table: Models and Trends
Practice Questions
View allWho coined the word 'atom'?
- A.Democritus
- B.Thomson
- C.E Rutherford
- D.John Dalton
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The Greek philosopher Democritus, working in the fifth century before the common era, argued that matter could be divided only up to a limit, and he called that smallest indivisible particle atomos, from which the word atom comes.
Read the full explanation →Who among the following discovered the neutrons?
- A.J. Chadwick
- B.E. Goldstein
- C.Neils Bohr
- D.Ernest Rutherford
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James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles and showing that the radiation produced consisted of neutral particles of nearly the same mass as the proton.
Read the full explanation →Rutherford's alpha-particle scattering experiment on a thin gold foil led to which conclusion?
- A.Electrons are embedded in a sphere of positive charge
- B.The atom is indivisible
- C.Electrons revolve in fixed permitted orbits
- D.Almost all the mass and the positive charge lie in a tiny nucleus
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Most alpha particles passed straight through the foil, a few were deflected through small angles and about one in twenty thousand bounced back.
Read the full explanation →The maximum number of electrons that can be accommodated in the M shell is:
- A.8
- B.2
- C.18
- D.32
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The capacity of a shell is given by the formula 2n squared, where n is the number of the shell counted outward from the nucleus.
Read the full explanation →Alkali metals are assigned which group in the Modern Periodic Table?
- A.Second group
- B.Eighteenth group
- C.Third group
- D.First group
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The alkali metals are lithium, sodium, potassium, rubidium, caesium and francium. Each has a single electron in its outermost shell, loses it readily to form a positive ion, and therefore stands in group 1 of the modern periodic table.
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